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ARB Staff Publishes Revised, Tiered Requirements for PHEV Conversions

The California Air Resources Board staff has published a supplemental report on revised requirements for plug-in hybrid electric vehicle conversion systems certification and installation.

In January, ARB staff presented certification test procedures for plug-in hybrid electric vehicles (PHEV) along with certification procedures for aftermarket PHEV conversion systems. The Board approved the exhaust and evaporative emissions test procedures as well as a new method for determining the range of fuel cell vehicles, but deferred a decision on the proposal for certification and warranty requirements for plug-in hybrid electric vehicles. (Earlier post.)

Concerned that the rule as proposed would have been too onerous for conversion start-ups, the Board directed staff to work more with the industry to develop a ruling that will do more to address the need to maintain a viable conversion industry.

The new approach being presented by the staff to the Board for consideration at the upcoming meeting 28-29 May creates a tiered approach to certification of PHEV conversion systems starting with application and engineering analysis that shows that there are no emission increases compared to the unconverted vehicle for the first ten units; requiring emission testing for the subsequent 90 units; and full certification for units thereafter. Warranty requirements for systems are also phased in.

  • Tier 1 (up to 10 conversion systems). The conversion system manufacturer’s application must address five main criteria: initial durability component data, a durability test plan for the converted vehicle, a consumer manual that shows at least a three-year or 50,000-mile warranty on the conversion system, a discussion on the process to maintain records of sales and installations, and an engineering analysis showing that conversion does not impact the emissions of the original vehicle.

  • Tier 2 (up to 100 conversion systems, inclusive of Tier 1 sales). Manufacturers must meet the first tier requirements along with three additional criteria: provide an onboard diagnostic compliance plan; submit a consumer manual which shows at least a warranty of 5 years or 75,000 miles; and submit emission test data which shows that the vehicle meets applicable emission standards, and does not trigger the onboard diagnostics malfunction indicator light (MIL) or diagnostic trouble code (DTC). During the second tier, ARB may perform confirmatory testing to verify the emission test data.

  • Tier 3 (101+ systems). For this tier, all of the requirements of the previous two tiers must be met along with proof that the following requirements are met:

    • The battery durability requirement is completed;
    • The durability of the conversion is proven to last through the vehicle’s useful life;
    • The converted vehicle must fully comply with onboard diagnostics;
    • The warranty must go through the remaining OEM warranty or the requirements in the second tier, whichever is longer; AND
    • The exhaust-, evaporative-, and on-board-vapor-recovery-refueling emission standards testing for hybrid electric vehicles are satisfactorily completed.

    The conversion system certification requirements in this tier are similar to what staff proposed at the January Board Hearing with the exception of the warranty. The original warranty proposal was equivalent to the OEM warranty: 15 years or 150,000 miles, and 10 years or 150,000 miles for the zero-emission energy-storage device. In the new proposal, the third tier requires a five-year or 75,000-mile warranty or the remaining OEM warranty whichever is greater, and thus reduces the warranty requirements.

Staff is proposing to limit use of this tiered certification program to the first 5,000 units industry-wide; in other words, after 5,000 vehicles are converted Tier 1 and Tier 2 options are no longer available.

The economic impacts of the proposal on manufacturers are largely the same as those in the original staff proposal; however they are spread out over the manufacturer’s first 100 vehicle conversions, providing conversion companies with a revenue stream to support certification costs.

Emission Impacts. ARB staff was careful to note that a PHEV conversion can be done without increasing a vehicle’s emissions, but that it must be done carefully to prevent significant increases to the original vehicle’s emissions. Staff has evaluated the potential emission impact of PHEV conversions.

Based on emissions testing performed on several converted PHEVs, a PHEV conversion system can easily increase the original vehicle’s exhaust emissions up to five times the amount its original certification value. In addition, the evaporative emissions can increase to up to 16 times the amount of its original certification value.

...Emission increases can occur with multiple engine starts during a single vehicle trip, and inadequate warming of the catalytic converter. In an HEV, the internal combustion engine starts and stops depending on user demand and the amount of energy stored in the energy storage device. If user demand exceeds the amount of energy stored, the vehicle’s computer will trigger the internal combustion engine start. Examples of this would include high acceleration rates, streets with high grades, or even simple driving habits if the battery is depleted. If this consumer demand occurs when the catalytic converter is not adequately warmed the emissions will be higher as well.

Converting hybrids to add plug in capability can increase evaporative emissions, as well. Careful consideration of the canister limitations must be evaluated. If the conversion prevents the internal combustion engine from purging the canister or the control system from recognizing when the internal combustion engine should purge the canister, emission breakthrough will occur.

ARB Staff Calculation of Potential Increase in Emissions
from 5,000 PHEV Conversions in TPY
PZEV 1.2 1.7 1.3 57 0.6
Potential PHEV conversion 5.8 8.6 13.8 287 2.9
Incremental Increase 4.6 6.9 12.5 230 2.3
Assumes 11,500 miles per year.




The ARB is an Air Resources Board in that the air is a shared resource and we all are interested in the quality of breathable air. They are NOT a consumer protection group and so they should NOT be dictating (which is what they are doing) the consumer warranty on anything.

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